Electrical Submersible Pump with Motor Winding Encapsulated in Bonded Ceramic

ABSTRACT

An electrical submersible pump assembly has a motor with a stator stack of limitations. The stack has slots through which magnet wires are wound. An encapsulate surrounds and bonds the magnet wires together within each slot. The encapsulate includes ceramic particles within a polymer adhesive matrix. The polymer matrix may be a fluoropolymer adhesive. Each of the magnet wires may have an electrical insulation layer surrounding a copper core. The ceramic particles are rounded and much smaller than a cross-sectional area of each of the magnet wires. At least some of the magnet wires may be in contact with a perimeter of the slot. The polymer matrix fills all voids within each of the slots. The ceramic particles may be porous.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to provisional application Ser. No.62/140,977, filed Mar. 31, 2015.

FIELD

The present disclosure relates to downhole pumping systems submersiblein well bore fluids. More specifically, the present disclosure relatesto an electrical submersible pump with motor windings that areencapsulated in a composition of ceramic and polymer.

BACKGROUND

Submersible pumping systems are often used in hydrocarbon producingwells for pumping fluids from within the well bore to the surface. Thesefluids are generally liquids made up of produced liquid hydrocarbon andoften water. One type of system used in this application employs anelectrical submersible pump (“ESP”). ESP's are typically disposed at theend of a length of production tubing and have an electrically poweredmotor. Often, electrical power may be supplied to the pump motor via anelectrical power cable from the surface that is strapped alongside thetubing.

ESP motors have stators with axially oriented slots and insulated magnetwires wound through the slots in a selected pattern. A sheet of aninsulation material is usually wrapped around each bundle of magnetwires within each of the slots. The magnet wires extend below a lowerend of the stator in loops spaced around a longitudinal axis of themotor. The magnet wires may be bonded in the slots with an epoxy resinto resist mechanical vibration during operation. In one technique,magnet wire leads are spliced to upper ends of three of the magnetwires. The magnet wire leads extend from the upper end of the stator tointernal contacts in a motor electrical plug-in receptacle. A dielectriclubricant fills the motor for lubricating bearings within the motor.

Typically, the pumping unit is disposed within the well bore just abovewhere perforations are made into a hydrocarbon producing zone. In thisposition the produced fluids flow past the outer surface of the pumpingmotor and absorb heat generated by the motor. In spite of the heattransfer between the fluid and the motor, the motor may still overheat.Overheating may be a problem when the fluid has a high viscosity, a lowspecific heat or a low thermal conductivity. This is typical of highlyviscous crude oils. Also, the motor may be forced to operate at anelevated temperature past its normal operating temperature to steaminjection wells. Elevated well temperatures can reduce motor life.Undesirable chemicals may be formed when the epoxy resin degrades underhigh temperature. These chemicals can damage the insulation layers ofthe magnet wires.

SUMMARY

An electrical submersible pumping (“ESP”) assembly has a pump driven byan electrical motor. The motor has a stack of stator laminations, thestator laminations having slots formed therethrough. Magnet wires arewound through the slots. An encapsulate bonds the magnet wires withineach of the slots together. The encapsulate comprises ceramic particlesbonded together within a polymer matrix.

The ceramic particles may have a size of 20 mesh to 140 mesh. Theceramic particles may be generally spherical. Each of the ceramicparticles has a cross-sectional area much smaller than a cross-sectionalarea of each of the magnet wires. The ceramic particles may be porous.

The polymer matrix is an electrical insulation material. The polymermatrix preferably comprises a fluoropolymer that is selected from agroup consisting of perfluoroalkoxy (“PFA”), fluorinated ethylenepropylene (“FEP”), polytetrafluoroethylene (“PTFE”), and combinationsthereof.

In the embodiment shown, each of the magnet wires comprises anelectrical insulation layer surrounding a copper core. Each of the slotshas a perimeter, and at least some of the magnet wires may be in contactwith the perimeter. The polymer matrix fills all voids within each ofthe slots.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having beenstated, others will become apparent as the description proceeds whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a transverse cross sectional view of a motor for use with anelectrical submersible pumping system, the motor being constructed inaccordance with this disclosure.

FIG. 2 is an enlarged view of one of the stator slots of the motor ofFIG. 1, schematically illustrating an encapsulate in the slot havingceramic particles dispersed within a polymer matrix.

FIG. 3 is a side perspective view of an example of a method ofencapsulating magnet wires in the motor of FIGS. 1 and 2.

FIG. 4 is a side partial sectional view of the motor of FIG. 1integrated with an electrical submersible pumping system and disposed ina wellbore.

While the invention will be described in connection with the preferredembodiments, it will be understood that it is not intended to limit theinvention to that embodiment. On the contrary, it is intended to coverall alternatives, modifications, and equivalents, as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION

The method and system of the present disclosure will now be describedmore fully hereinafter with reference to the accompanying drawings inwhich embodiments are shown. The method and system of the presentdisclosure may be in many different forms and should not be construed aslimited to the illustrated embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey its scope to those skilled in the art.Like numbers refer to like elements throughout. In an embodiment, usageof the term “about” includes +/−5% of the cited magnitude. In anembodiment, usage of the term “substantially” includes +/−5% of thecited magnitude.

It is to be further understood that the scope of the present disclosureis not limited to the exact details of construction, operation, exactmaterials, or embodiments shown and described, as modifications andequivalents will be apparent to one skilled in the art. In the drawingsand specification, there have been disclosed illustrative embodimentsand, although specific terms are employed, they are used in a genericand descriptive sense only and not for the purpose of limitation.

FIG. 1 shows an axial partial sectional view of an upper end of a motor10 for use with an electrical submersible pumping system (“ESP”). Themotor 10 is equipped with a generally cylindrical housing 12 whichcovers and protects components of the motor 10 against harsh downholeconditions, and provides an external support in which the components arecontained. Motor 10 will typically be filled with a liquid dielectricmotor lubricant. Illustrated within housing 12 is a stator assembly 14,which includes a stator stack 16 made up of a series of laminations thatare coaxially stacked together. Each lamination is a typically a thin,steel disc. The laminations of stator stack 16 have central openings 17that define a bore of stator assembly 14. An annular ring 18 shown seton an upper surface of stator slack 16 has an inner diameter less thanan outer diameter of stator stack 16 and retains stack 16 within housing12.

A series of slots 20 are formed axially through each of the laminationsin stack 16 and which extend along a length of stack 16. Slots 20 asshown are formed equidistant apart from one another, extendingcircumferentially around the bore of the stator slack 16. Referring toFIG. 2, each slot 20 has a perimeter 21 that may be generallytrapezoidal in shape, as shown. An opening (not shown) may lead fromeach slot 20 to central opening 17. Alternately, each slot 20 may becompletely enclosed by its perimeter 21.

A number of motor or magnet wires 22 are wound along the length of eachof the slots 20. Normally, motor 10 (FIG. 1) is a three-phase motor andwill have three separate magnet wires 22. Each magnet wire 22 extendsthe length of stator assembly 14 and has multiple turns within each slot20. Preferably, each magnet wire 22 has a metal core 22 a, normallycopper, that is encased in a high temperature electrical insulationlayer 22 b.

An encapsulate 24 surrounds and rigidly bonds the magnet wires 22together within each slot 20 and forms a protective coating around themagnet wires 22. In this embodiment, there is no liner surrounding thebundle of magnet wires 22 in each slot 20; rather encapsulate 24 andmagnet wires 22 completely fill each slot 20. Part of encapsulate 24will be bonded to and in contact with perimeter 21 of each slot 20.Also, some of the magnet wires 22 will be in contact with slot perimeter21.

Encapsulate 24 is made up of a mixture of ceramic particles 25 bondedtogether by a polymer matrix 27. Ceramic particles 25 are dispersedthroughout polymer matrix 27. Ceramic particles 25 are formed of a hardmaterial with high electrical insulation properties. Ceramic particles25 may be porous to the dielectric motor lubricant contained withinmotor 10 so as to increase the rate of heat transfer from motor 10.

Ceramic particles 25 have cross-sectional dimensions much smaller thanthe cross-sectional dimension of each magnet wire 22. For example,ceramic particles 25 may be in a particle range size from about 20 meshto about 140 mesh. In one optional embodiment, ceramic particles 25 aregenerally rounded or spherical and do not have sharp edges. The roundedshape of the ceramic particles 25 reduces the chances for damagingmagnet wire insulation layers 22 b.

Ceramic particles 25 may comprise proppants or micro-spheres, such asthose used for downhole gravel packing having a trade name ofCarboaccucast®, and which may be commercially available from the CarboCorporation, 575 N. Dairy Ashford Rd, Suite 300, Houston, Tex., 77079,(281) 921 6400. In a non-limiting example, ceramic particles 25 maycomprise Carboaccucast® ID50 having a particle size of from about 50mesh to about 100 mesh. Alternate embodiments exist wherein ceramicparticles 25 comprise alumina (99.9% Al2O3), aluminum silicate, Al2SiO5,berillia (99% BeO), boron nitride, BN, cordierite, Mg2Al4Si5O18,forsterite, mg2SiO4, porcelain, steatite, Mg3Si4O11.H2O, titanates ofMg, Ca, Sr, Ba, and Pb, barium titanate, glass bonded, zirconia, ZrO2,fused silica, SiO2, micas, muscovite, ruby, natural, phlogopite, amber,natural, fluorophlogopite, synthetic, glass-bonded mica, andcombinations thereof.

Polymer matrix 27 is formed of a polymer adhesive that heat cures afterfilling each slot 20. Example polymer adhesives for polymer matrix 27include fluoropolymers. Example fluoropolymers for polymer matrix 27include perfluoroalkoxy alkanes (“PFA”), fluorinated ethylene propylene(“FEP”), and polytetrafluoroethylene (“PTFE”). Preferably, polymermatrix 27 has good chemical resistance properties at elevatedtemperatures. Elevated temperatures are those that can typically occurdownhole, and may be those that exceed about 150° F.

One method of manufacturing polymer matrix 27 employs a fluoropolymersupplied as a powder that has a particle size ranging from about 20micron to about 200 micron. In a non-limiting example, polymer matrix 27may include a fluoro-polymer powdered binder NC-1500 available fromDaikin Chemicals, 20 Olympic Drive Orangeburg, N.Y. 10962,http://ww.daikin-america.com/, and which is a thermal-fusible FEP basedfine powder having a particle size of from about 30 microns to about 60microns.

Referring again to FIG. 1, a rotor assembly 26 is shown circumscribed bystator assembly 14, where the rotor assembly 26 rotates with respect tostator assembly 14. Rotor assembly 26 includes several rotor stacks 28(only one shown) axially separated from each other by radial bearings.Rotor stack 28, similar to stator slack 16, is made up of a number ofrotor laminations or steel discs that are stacked on top of one anotherin a coaxial arrangement. Slots 30 are formed axially through each ofthe rotor laminations, so that when the laminations are stacked, theslots 30 extend through the entire length of the rotor stack 28. Slots30 are shown substantially equidistant apart from one another atmultiple angular locations around the rotor stack 28. Elongate rotorbars 32 are set in slots 30, wherein in one example the rotor bars 32include a magnetic material. Thus, in one example, energizing the magnetwires 22 with an electrical current creates an alternatingelectromagnetic field (not shown). The rotor bars 32 are responsive tothe electromagnetic field thereby causing rotation of the rotor assembly26. Coaxial within the rotor assembly 26 is an elongate shall 34 thatcouples to and rotates with the rotor assembly 26.

In one non-limiting example, the mixture of ceramic particles 23 andpolymer powder for polymer matrix 27 includes about 100 parts of ceramicparticles 25 and about 30 parts of polymer matrix 27 powder. Ceramicparticles 25 may have a size of about 50 mesh to about 100 mesh, and thepowder for polymer matrix 27 may have a particle size of about 30microns to about 60 microns. Yet further optionally, the polymer matrix27 may include a chemical resistant fluoro-polymeric powder, such asFEP. Further optionally in this example, new stainless steel componentsare installed in the stator and end attachments, and the slots 20 in thestator stack 16 are filled with the mixture of ceramic particles 25 andpowder for polymer matrix 27.

Schematically illustrated in FIG. 3 is one example of how theencapsulate 24 of FIGS. 1 and 2 can be formed within slots 20. As shown,a mixture 38 of ceramic particles 25 and powdered polymer matrix 27 iscombined within a container 36 having an outlet 37. Mixture 38 exits theoutlet 37 and enters a shroud 40 that is set over the upper end of motor10. At the opposite end of motor 10 is a vacuum system 41 that draws airfrom within the motor 10, and thus the slots 20 (FIGS. 1 and 2), therebydrawing in mixture 38 to fill all voids and interstices that may existbetween the magnet wires 22 in the slots 20 (FIGS. 1 and 2). Optionally,a filter 42 may be within vacuum system 41 for blocking ceramicparticles 27 or the powders of polymer matrix 27 from exiting the lowerend of vacuum system 41. In one embodiment filter 42 comprises a 100mesh steel screen for capturing ceramic particles 25 and polymer matrix27 powders that may make their way through the entire length of motor10. In one alternative, a vacuum pump 44 is included on the lower end ofvacuum system 41, wherein a hose connects vacuum pump 44 to the lowerend of pump 10 so that the vacuum pump 44 can apply suction to the lowerend of the slots 20. A mechanical shaker (not shown), can be used tofurther ensure mixture 38 fills any remaining voids in the slots 20.

After mixture 38 of ceramic particles 25 and polymer matrix 27 powdersfill slots 20 around magnet wires 22, mixture 38 can be heated. Theheating may be done either by heating the entire motor 10 or byconducting electricity through magnet wires 22 for heating the mixture38. In one example, a melting point of the powders of polymer matrix 27is about 260° C. to about 350° C.; thus the mixture 38 is heated to atfeast this temperature, thereby melting the powders of polymer matrix27. The heating and subsequent cooling causes bonding of ceramicparticles 25 within polymer matrix 27 to magnet wires 22, forming asolid, rigid encapsulate 24 within slots 20 for projecting wires 22. Theheating does not affect ceramic particles 25.

Optionally, heating of the entire motor 10 can take place within a hightemperature tubular oven 43. In a non-limiting example, the motor 10 isheated for a period of time up to about 5 hours, and the upper and loweropenings of slots 20 are plugged to retain mixture 38 in the slots 20.Yet further optionally, a nitrogen blanket is applied to the motor 10 toremove volatiles released during heating. Melting, then cooling thepolymer matrix 27 powders forms an integrated tough structural bondingmaterial that secures the magnet wires 22 in place within slots 20. Asindicated above, the presence of ceramic particles 25 within theencapsulate 24 creates a porosity for encapsulate 24, which increasesheat transfer away from motor.

Shown in partial side sectional view in FIG. 4 is one example of themotor 10 used in conjunction with an electrical submersible pump (ESP)system or assembly 45. Here the ESP system 45 is disposed in a wellbore46 on a lower end of a suing of production tubing 48. An upper end ofproduction tubing 48 connects to a wellhead assembly 50, shown cappingan upper end of wellbore 46. Motor 10 couples to a pump 58, which isshown provided on an upper end of ESP system 45. Shaft 34 connects toimpellers 54 (shown in phantom view) within pump 58. Pump 58 pumps wellfluid from within wellbore 46 so it may be discharged to the productiontubing 48 and pumped to the wellhead assembly 50. A seal section 56 isprovided between the pump 52 and motor 10 for equalizing pressure withinthe ESP system 45 with the hydrostatic pressure of well fluid inwellbore 46. An intake 58 is shown formed through a housing of the pump52 so that fluid within wellbore 46 can make its way to the impellers 54for pressurization and delivery to production tubing 48. In thisexample, the fluids pressurized by the ESP system 45 are produced from aformation 60 that is intersected by the wellbore 46.

The present invention described herein is well adapted to carry out theobjects and attain the ends and advantages mentioned, as well as othersinherent therein. The chemically inert encapsulation of the motor wiresreplaces chemically instable epoxy resin. While a presently preferredembodiment of the invention has been given for purposes of disclosure,numerous changes exist in the details of procedures for accomplishingthe desired results. These and other similar modifications will readilysuggest themselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims.

1. An electrical submersible pumping (“ESP”) assembly comprising: a pumpdriven by an electrical motor; the motor having a stack of statorlaminations, the stator laminations having slots formed therethrough;magnet wires wound through the slots; and an encapsulate that bonds themagnet wires within each of the slots together, the encapsulatecomprising ceramic particles bonded together within a polymer matrix. 2.The ESP assembly of claim 1, wherein the ceramic particles have a sizeof 20 mesh to 140 mesh.
 3. The ESP assembly of claim 1, wherein thepolymer matrix comprises a fluoropolymer that is selected from a groupconsisting of perfluoroalkoxy (“PFA”), fluorinated ethylene propylene(“FEP”), polytetrafluoroethylene (“PTFE”), and combinations thereof. 4.The ESP assembly of claim 1, wherein each of the magnet wires comprisesan electrical insulation layer surrounding a copper core.
 5. The ESPassembly of claim 1, wherein the ceramic particles are generallyspherical.
 6. The ESP assembly of claim 1, wherein each of the ceramicparticles has a cross-sectional area much smaller than a cross-sectionalarea of each of the magnet wires.
 7. The ESP assembly of claim 1,wherein: each of the slots has a perimeter; and at least some of themagnet wires are in contact with the perimeter.
 8. The ESP assembly ofclaim 1, wherein: the polymer matrix fills all voids within each of theslots.
 9. The ESP assembly of claim 1, wherein: the polymer matrix isformed of an electrical insulation material.
 10. The ESP assembly ofclaim 1, wherein the ceramic particles are porous.
 11. An electricalsubmersible pumping (ESP) assembly, comprising: a pump driven by anelectrical motor, the motor comprising: a housing having a longitudinalaxis; a slack of stator laminations stacked on each other within thehousing, the stack of stator laminations having an axial opening and aplurality of slots spaced circumferentially around the opening; magnetwires wound through each of the slots in the stack, each of the magnetwires having a conductive core encased in an electrical insulationlayer; a polymer matrix of an electrical insulation material bonding themagnet wires within each of the slots together; and ceramic particlesdispersed throughout and bonded within the polymer matrix.
 12. The ESPassembly according to claim 11, wherein: the polymer matrix comprises afluoropolymer adhesive.
 13. The ESP assembly according to claim 11,wherein: the ceramic particles have a size of 20 mesh to 140 mesh. 14.The ESP assembly of claim 11, wherein the polymer matrix comprises afluoropolymer that is selected from a group consisting ofperfluoroalkoxy (“PFA”), fluorinated ethylene propylene (“FEP”),polytetrafluoroethylene (“PTFE”), and combinations thereof.
 15. The ESPassembly of claim 11, wherein the ceramic particles are generallyspherical.
 16. The ESP assembly of claim 11, wherein: each of the slotshas a perimeter; at least some of the magnet wires are in contact withthe perimeter; and a portion of the polymer matrix is in contact withthe perimeter.
 17. An electrical submersible pumping (ESP) assembly,comprising: a pump driven by an electrical motor, the motor comprising:a housing having a longitudinal axis; a stack of stator laminationsstacked on each other within the housing; the stack of statorlaminations having an axial opening and a plurality of slots spacedcircumferentially around the opening; magnet wires wound through each ofthe slots in the stack, each of the magnet wires having a conductivecore encased in an electrical insulation layer; a rotor extending alongthe axis through the opening in the stack; a fluoropolymer adhesivematrix bonding all of the magnet wires within each of the slotstogether; and ceramic particles dispersed throughout and bonded withinthe fluoropolymer adhesive matrix, each of the ceramic particles beinggenerally spherical and having a much smaller cross-sectional than eachof the magnet wires.
 18. The ESP assembly of claim 17, wherein thefluoropolymer adhesive matrix comprises a fluoropolymer that is selectedfrom a group consisting of perfluoroalkoxy (“PFA”), fluorinated ethylenepropylene (“FEP”), polytetrafluoroethylene (“PTFE”), and combinationsthereof.
 19. The ESP assembly of claim 17, wherein: each of the slotshas a perimeter; at least some of the magnet wires are in contact withthe perimeter; and the fluoropolymer adhesive matrix is bonded to theperimeter and fills all voids in each of the slots.
 20. The ESP assemblyof claim 17, wherein: the ceramic particles are porous.